1. Field of the Invention
This invention relates to an apparatus for judging whether an uncut lens should be machined or not and a lens grinding machine or lens edge grinding machine having the same, in which a judgment is made as to whether a lens having a desired lens frame configuration from an uncut lens before the uncut lens is subjected to grinding treatment by the lens grinding machine.
2. Description of the Prior Art
Heretofore, a lens grinding machine is used for grinding an uncut lens (material lens) into a lens frame configuration can be obtained of a spectacle frame to which the lens is to be enframed. Before the uncut lens is ground by the lens grinding machine, the axis (or center axis) of a sucking disk or sucking device is brought into alignment with the optical center of the uncut lens and then the sucking disk is allowed to be sucked and attached to the uncut lens. The sucking disk has a shaft portion for mounting to a rotating shaft of the lens grinding machine and a rubber cup for sucking the lens. When this sucking disk is sucked and attached to the lens, the diameter of the sucking disk becomes generally equal to or slightly greater than the diameter of the lens mounting shaft.
When the peripheral edge of the material lens is ground into the lens frame configuration, a shaft portion of the sucking disk is coaxially held by the lens rotating shaft of the lens grinding machine, the peripheral edge portion of the uncut lens is ground by a grinder which is rotating at a high speed while the rotational axis of the lens is being rotated. At that time, it is a usual practice that the peripheral edge portion of the uncut lens is ground such that the optical center or optical axis of the lens has a desired displacement relative to the geometrical center of lens frame.
Also, today, the lens machining processes are divided or specialized. For example, the lens machining processes include a dot marking process to a material lens, a sucking process for sucking and attaching the sucking disk to the material lens accompanying an aligning or centering process of the material lens, and a grinding process made by a lens grinding machine after the material lens has been sucked by the sucking disk.
Today, where the lens machining processes are such specialized as mentioned, there is such a possibility as to invite a failure in that it is found that a desired lens frame configuration cannot be obtained only after the material lens has actually been machined. However, if we take into consideration such a serious fact as that a material lens once failed in machining is usually unable to be machined again, this can be a vital loss to a spectacle store.
In order to avoid such an undesirable incidence, it also becomes an important work to check as to whether a desired lens frame configuration (outer configuration) can be obtained or not, if an uncut lens is subjected to grinding treatment made by a lens grinding machine.
Heretofore, this checking operation was performed using a template which was obtained by machining a material plate copying the lens frame configuration before the sucking disk is sucked and attached to the uncut lens. Moreover, when in such checking, the template and the uncut lens were superimposed upon each other in such a manner as that the geometrical center of the template is moved from the optical center of the uncut lens by a desired amount, and it was checked whether the peripheral portion of the template is expanded from the peripheral edge of the uncut lens. And, when the peripheral portion of the template is expanded from the peripheral portion of the uncut lens, the uncut lens was judged as being not large enough to be machined into a template configuration and another selection of an uncut lens of a greater diameter was requested.
In recent years, there is a spectacle so called "Kanime lens (or pin face lens)" which is for the exclusive use of a shortsighted person and the width of a lens frame of which is extremely narrow in the vertical direction.
If an attempt is made to obtain such kanime lens or pin face lens from a circular-shaped material lens (uncut lens) by means of grinding using a lens grinding machine, it occurs a so-called "machining interference" occurs in which the sucking disk sucked and attached to the material lens is ground by the lens grinder. When this machining interference is grave, there is such a fear as that even a mounting member of the sucking disk is also contacted with the lens grinder to break the lens grinding machine itself.
Also, in case a material lens is to be machined into a general lens frame configuration other than the kanime lens, the machining interference also occurs when the displacement (usually called the "inwardly sided amount" or "upwardly sided amount") between the optical center of the uncut lens and the geometrical center of the lens frame is large.
The conventional method for checking the "machining interference" before it occurs is performed in such a manner as that a template obtained by copying a lens frame of a spectacle frame and an uncut lens are physically superposed one upon the other taking into consideration the displacing amount thereof, then the sucking disk is sucked and attached onto the uncut lens such that the center of the sucking disk is brought into alignment with the geometrical center of the template, and then it is checked whether the sucking disk expands from the template.
However, the conventional method for checking an outer diameter machinability using a template and the conventional method for checking the machining interference are very complicated to put into practice. Moreover, if the sucking disk is sucked and attached to the lens before the machining interference is checked, a dot mark on the uncut lens serving as a target mark for centering the displacing position between the uncut lens and the template is hidden by the sucking disk and, therefore, the centering operation of the displacing position thereof becomes impossible to carry out. As a result, it becomes impossible to carry out the checking as for machining interference.
On the other hand, a lens grinding machine requiring no template came into practice in recent years. As such lens grinding machine, there is known, for example, a "non-former lens grinding machine" or a "patternless lens grinding machine" like a lens grinding machine as disclosed in detail in a Japanese Patent Application No. 60-115079 filed earlier by the present applicant.
In this new lens grinding machine, the configuration of a lens frame of a spectacle frame is measured by a frame configuration measuring apparatus as one element of the constituent system of the lens grinding machine in order to obtain the distance (radius vector .rho..sub.1) from the geometrical center of the lens frame to the V-edge groove of the lens frame every predetermined angle .theta..sub.1. At that time, the radius vector information (.rho..sub.1, .theta..sub.1) (i=1, 2, 3, . . . N here) is obtained as an electric signal by mechanical/electrical measurement. Thereafter, the lens machining radius vector (.sub.k .rho..sub.1, .sub.k .theta..sub.1) (i=1, 2, 3, . . . N here) is found by adding the displacing amount between the uncut lens and the lens frame to this electric signal, and the material lens is ground with reference to the lens machining radius vector. The sucking disk is normally sucked and attached to the optical center of the material lens.
The lens grinding machine disclosed in the above-mentioned Japanese Patent Application No. Sho 60-115079 has a lens configuration measuring apparatus for measuring the configuration of a material lens. And this lens grinding machine is designed such that fillers are brought into abut engagement with front and rear refracting surfaces of the uncut lens along the radius vector orbit with reference to the lens machining radius vector (.sub.k .rho..sub.1, .sub.k .theta..sub.1), and when these fillers are disengaged from the uncut lens, it is automatically judged that a desired lens frame configuration from this material lens and a warning is issued.
In such non-former lens grinding machines, physical existence as a template does not exist, but only configuration data of the lens frame exists as an electric signal. Accordingly, it is impossible to check whether the machining interference is occurred or not by visually confirming the mutual positional relation between the lens frame configuration data and the sucking disks sucked and attached to the uncut lens.
Also in this non-former lens grinding machine, although it can overcome the complication of the checking work as to whether the outer configuration of the material lens can be machined, such judgment can be made only after the material lens has been set to the lens rotational shaft. Accordingly, in case it was judged that the material lens cannot be machined, this material lens is required to be replaced with a new material lens having a comparatively large diameter after the checking work has been finished to the material lens which was still in the half-way of the machining process. Moreover, at that time, it is required that the machining worker perform the centering work from the beginning all over again or the worker perform the centering work again to a new material lens having a larger diameter. This naturally turns out the merit of specialization to demerit.